OK, let's crack this. We're given 635 and our task is to multiply it by 255. Essentially, we'll be adding 635 to itself 255 times.
Step 1: 0 + 635 = 635
Step 2: 635 + 635 = 1270
Step 3: 1270 + 635 = 1905
Step 4: 1905 + 635 = 2540
Step 5: 2540 + 635 = 3175
Step 6: 3175 + 635 = 3810
Step 7: 3810 + 635 = 4445
Step 8: 4445 + 635 = 5080
Step 9: 5080 + 635 = 5715
Step 10: 5715 + 635 = 6350
Step 11: 6350 + 635 = 6985
Step 12: 6985 + 635 = 7620
Step 13: 7620 + 635 = 8255
Step 14: 8255 + 635 = 8890
Step 15: 8890 + 635 = 9525
Step 16: 9525 + 635 = 10160
Step 17: 10160 + 635 = 10795
Step 18: 10795 + 635 = 11430
Step 19: 11430 + 635 = 12065
Step 20: 12065 + 635 = 12700
Step 21: 12700 + 635 = 13335
Step 22: 13335 + 635 = 13970
Step 23: 13970 + 635 = 14605
Step 24: 14605 + 635 = 15240
Step 25: 15240 + 635 = 15875
Step 26: 15875 + 635 = 16510
Step 27: 16510 + 635 = 17145
Step 28: 17145 + 635 = 17780
Step 29: 17780 + 635 = 18415
Step 30: 18415 + 635 = 19050
Step 31: 19050 + 635 = 19685
Step 32: 19685 + 635 = 20320
Step 33: 20320 + 635 = 20955
Step 34: 20955 + 635 = 21590
Step 35: 21590 + 635 = 22225
Step 36: 22225 + 635 = 22860
Step 37: 22860 + 635 = 23495
Step 38: 23495 + 635 = 24130
Step 39: 24130 + 635 = 24765
Step 40: 24765 + 635 = 25400
Step 41: 25400 + 635 = 26035
Step 42: 26035 + 635 = 26670
Step 43: 26670 + 635 = 27305
Step 44: 27305 + 635 = 27940
Step 45: 27940 + 635 = 28575
Step 46: 28575 + 635 = 29210
Step 47: 29210 + 635 = 29845
Step 48: 29845 + 635 = 30480
Step 49: 30480 + 635 = 31115
Step 50: 31115 + 635 = 31750
Step 51: 31750 + 635 = 32385
Step 52: 32385 + 635 = 33020
Step 53: 33020 + 635 = 33655
Step 54: 33655 + 635 = 34290
Step 55: 34290 + 635 = 34925
Step 56: 34925 + 635 = 35560
Step 57: 35560 + 635 = 36195
Step 58: 36195 + 635 = 36830
Step 59: 36830 + 635 = 37465
Step 60: 37465 + 635 = 38100
Step 61: 38100 + 635 = 38735
Step 62: 38735 + 635 = 39370
Step 63: 39370 + 635 = 40005
Step 64: 40005 + 635 = 40640
Step 65: 40640 + 635 = 41275
Step 66: 41275 + 635 = 41910
Step 67: 41910 + 635 = 42545
Step 68: 42545 + 635 = 43180
Step 69: 43180 + 635 = 43815
Step 70: 43815 + 635 = 44450
Step 71: 44450 + 635 = 45085
Step 72: 45085 + 635 = 45720
Step 73: 45720 + 635 = 46355
Step 74: 46355 + 635 = 46990
Step 75: 46990 + 635 = 47625
Step 76: 47625 + 635 = 48260
Step 77: 48260 + 635 = 48895
Step 78: 48895 + 635 = 49530
Step 79: 49530 + 635 = 50165
Step 80: 50165 + 635 = 50800
Step 81: 50800 + 635 = 51435
Step 82: 51435 + 635 = 52070
Step 83: 52070 + 635 = 52705
Step 84: 52705 + 635 = 53340
Step 85: 53340 + 635 = 53975
Step 86: 53975 + 635 = 54610
Step 87: 54610 + 635 = 55245
Step 88: 55245 + 635 = 55880
Step 89: 55880 + 635 = 56515
Step 90: 56515 + 635 = 57150
Step 91: 57150 + 635 = 57785
Step 92: 57785 + 635 = 58420
Step 93: 58420 + 635 = 59055
Step 94: 59055 + 635 = 59690
Step 95: 59690 + 635 = 60325
Step 96: 60325 + 635 = 60960
Step 97: 60960 + 635 = 61595
Step 98: 61595 + 635 = 62230
Step 99: 62230 + 635 = 62865
Step 100: 62865 + 635 = 63500
Step 101: 63500 + 635 = 64135
Step 102: 64135 + 635 = 64770
Step 103: 64770 + 635 = 65405
Step 104: 65405 + 635 = 66040
Step 105: 66040 + 635 = 66675
Step 106: 66675 + 635 = 67310
Step 107: 67310 + 635 = 67945
Step 108: 67945 + 635 = 68580
Step 109: 68580 + 635 = 69215
Step 110: 69215 + 635 = 69850
Step 111: 69850 + 635 = 70485
Step 112: 70485 + 635 = 71120
Step 113: 71120 + 635 = 71755
Step 114: 71755 + 635 = 72390
Step 115: 72390 + 635 = 73025
Step 116: 73025 + 635 = 73660
Step 117: 73660 + 635 = 74295
Step 118: 74295 + 635 = 74930
Step 119: 74930 + 635 = 75565
Step 120: 75565 + 635 = 76200
Step 121: 76200 + 635 = 76835
Step 122: 76835 + 635 = 77470
Step 123: 77470 + 635 = 78105
Step 124: 78105 + 635 = 78740
Step 125: 78740 + 635 = 79375
Step 126: 79375 + 635 = 80010
Step 127: 80010 + 635 = 80645
Step 128: 80645 + 635 = 81280
Step 129: 81280 + 635 = 81915
Step 130: 81915 + 635 = 82550
Step 131: 82550 + 635 = 83185
Step 132: 83185 + 635 = 83820
Step 133: 83820 + 635 = 84455
Step 134: 84455 + 635 = 85090
Step 135: 85090 + 635 = 85725
Step 136: 85725 + 635 = 86360
Step 137: 86360 + 635 = 86995
Step 138: 86995 + 635 = 87630
Step 139: 87630 + 635 = 88265
Step 140: 88265 + 635 = 88900
Step 141: 88900 + 635 = 89535
Step 142: 89535 + 635 = 90170
Step 143: 90170 + 635 = 90805
Step 144: 90805 + 635 = 91440
Step 145: 91440 + 635 = 92075
Step 146: 92075 + 635 = 92710
Step 147: 92710 + 635 = 93345
Step 148: 93345 + 635 = 93980
Step 149: 93980 + 635 = 94615
Step 150: 94615 + 635 = 95250
Step 151: 95250 + 635 = 95885
Step 152: 95885 + 635 = 96520
Step 153: 96520 + 635 = 97155
Step 154: 97155 + 635 = 97790
Step 155: 97790 + 635 = 98425
Step 156: 98425 + 635 = 99060
Step 157: 99060 + 635 = 99695
Step 158: 99695 + 635 = 100330
Step 159: 100330 + 635 = 100965
Step 160: 100965 + 635 = 101600
Step 161: 101600 + 635 = 102235
Step 162: 102235 + 635 = 102870
Step 163: 102870 + 635 = 103505
Step 164: 103505 + 635 = 104140
Step 165: 104140 + 635 = 104775
Step 166: 104775 + 635 = 105410
Step 167: 105410 + 635 = 106045
Step 168: 106045 + 635 = 106680
Step 169: 106680 + 635 = 107315
Step 170: 107315 + 635 = 107950
Step 171: 107950 + 635 = 108585
Step 172: 108585 + 635 = 109220
Step 173: 109220 + 635 = 109855
Step 174: 109855 + 635 = 110490
Step 175: 110490 + 635 = 111125
Step 176: 111125 + 635 = 111760
Step 177: 111760 + 635 = 112395
Step 178: 112395 + 635 = 113030
Step 179: 113030 + 635 = 113665
Step 180: 113665 + 635 = 114300
Step 181: 114300 + 635 = 114935
Step 182: 114935 + 635 = 115570
Step 183: 115570 + 635 = 116205
Step 184: 116205 + 635 = 116840
Step 185: 116840 + 635 = 117475
Step 186: 117475 + 635 = 118110
Step 187: 118110 + 635 = 118745
Step 188: 118745 + 635 = 119380
Step 189: 119380 + 635 = 120015
Step 190: 120015 + 635 = 120650
Step 191: 120650 + 635 = 121285
Step 192: 121285 + 635 = 121920
Step 193: 121920 + 635 = 122555
Step 194: 122555 + 635 = 123190
Step 195: 123190 + 635 = 123825
Step 196: 123825 + 635 = 124460
Step 197: 124460 + 635 = 125095
Step 198: 125095 + 635 = 125730
Step 199: 125730 + 635 = 126365
Step 200: 126365 + 635 = 127000
Step 201: 127000 + 635 = 127635
Step 202: 127635 + 635 = 128270
Step 203: 128270 + 635 = 128905
Step 204: 128905 + 635 = 129540
Step 205: 129540 + 635 = 130175
Step 206: 130175 + 635 = 130810
Step 207: 130810 + 635 = 131445
Step 208: 131445 + 635 = 132080
Step 209: 132080 + 635 = 132715
Step 210: 132715 + 635 = 133350
Step 211: 133350 + 635 = 133985
Step 212: 133985 + 635 = 134620
Step 213: 134620 + 635 = 135255
Step 214: 135255 + 635 = 135890
Step 215: 135890 + 635 = 136525
Step 216: 136525 + 635 = 137160
Step 217: 137160 + 635 = 137795
Step 218: 137795 + 635 = 138430
Step 219: 138430 + 635 = 139065
Step 220: 139065 + 635 = 139700
Step 221: 139700 + 635 = 140335
Step 222: 140335 + 635 = 140970
Step 223: 140970 + 635 = 141605
Step 224: 141605 + 635 = 142240
Step 225: 142240 + 635 = 142875
Step 226: 142875 + 635 = 143510
Step 227: 143510 + 635 = 144145
Step 228: 144145 + 635 = 144780
Step 229: 144780 + 635 = 145415
Step 230: 145415 + 635 = 146050
Step 231: 146050 + 635 = 146685
Step 232: 146685 + 635 = 147320
Step 233: 147320 + 635 = 147955
Step 234: 147955 + 635 = 148590
Step 235: 148590 + 635 = 149225
Step 236: 149225 + 635 = 149860
Step 237: 149860 + 635 = 150495
Step 238: 150495 + 635 = 151130
Step 239: 151130 + 635 = 151765
Step 240: 151765 + 635 = 152400
Step 241: 152400 + 635 = 153035
Step 242: 153035 + 635 = 153670
Step 243: 153670 + 635 = 154305
Step 244: 154305 + 635 = 154940
Step 245: 154940 + 635 = 155575
Step 246: 155575 + 635 = 156210
Step 247: 156210 + 635 = 156845
Step 248: 156845 + 635 = 157480
Step 249: 157480 + 635 = 158115
Step 250: 158115 + 635 = 158750
Step 251: 158750 + 635 = 159385
Step 252: 159385 + 635 = 160020
Step 253: 160020 + 635 = 160655
Step 254: 160655 + 635 = 161290
Step 255: 161290 + 635 = 161925

So, 635*255 = 161925